Antenna system



Aug 3i, w48. H. @..BUSIGNIES Em 2,448,017

ANTENNA SYSTEM Filed April 17, 1945 INVENTORB HENRI 6. Basle/wes nr/fm mm1/10 Patented Aug. 3l, 1943 FFHCE ANTENNA SYSTEM Application April 17, 1945. Serial No. 588,8,48

s calms. l

The present invention relates to antenna systems and particularly to antenna systems adapted for use in direction finding equipment.

Heretofore in antenna systems it has been customary to provide separate antenna units for the reception of vertically and horizontally polarized waves. In direction finding equipment the use of two such antenna units introduces interference and distortion of the directional pattern of one of the units by the other. I! the separate units are separately coupled to the direction finding equipment as by means of a direction finding receiver it further becomes necessary to add switching devicesA to continuously switch from one unit to the other in order to make certain that reception is being had of differently polarized waves.

An object of the present invention is the provision of an antenna system in which a single antenna unit serves for both horizontally and vertically polarized waves.

Another object of the present invention is the provision in a direction finding system of an antenna adapted to receive both vertically and horizontally polarized waves simultaneously.

A further object of the present invention is the provision of an antenna unit oi the type hereinabove described which provides a satisfactory pattern of reception for both horizontally and vertically polarized waves.

Other and further objects of the present invention will become apparent an-d the invention will be best understood from the following description of an embodiment thereof reference being had to the drawings in which:

Fig. i is a schematic diagram of a direction finding system embodying our invention;

Fig. 2 is a front elevation of an embodiment of an antenna system according to our invention, and

Figs. 3 and 4 are polar diagrams of the actual reception patterns received with an antenna of the type disclosed in Fig. 2 for horizontal and vertical reception respectively.

Referring now to Fig. 1, the direction finding system there illustrated includes an antenna system generally designated by the numeral i consisting of two dipoles 2 and 3 respectively, arranged in front of a reflector il. The system is of the null detection type and accordingly the dpoles are connected in phase opposition, with the transmission lines 5 and 8, connecting the dipoles il and 3, effectively cross-connected as will be seen from said figure. The midpoints of lines 5 and 6 are connected by means of a dual transmission line 'I to a balance box 8 which converts from the dual transmission line 1 to a single coaxial line t, the line 9 in turn being connected to the direction finding receiver I0 in whose output an indicator II, such as for example an oscilloscope may be provided.

The dipoles 2 and 3 are Preferably adapted for wide band reception. Each of the dipoles 2 and il preferably consists of two arms I2 (Fig. 2), each having a cylindrical portion I3 merging into a conically tapered portion I4, the ends of which conically tapered portions I4 are mounted close together. The tapering of these portions I4 reduces the capacity between the arms. 'I'he dipoles 2 and 3 are preferably mounted on the reflecting screen 4 and spaced a distance of wavelength or less from the screen. One of the dipoles may have an electrical length of 360; usually it is preferred that they have the length of 180. The distance between the centers of the two dipoles is preferably 180 or less. All these foregoing dimensions are in terms of the mean frequency of the band of frequencies over which said system is designed to operate.

The reflecting screen 4 is a planar member, vertically extending, and may be a solid sheet of conducting material or if desired may be made in the form of a meshed screen or grill work.

It is preferably substantially larger than the length of the dipole such as for example twice as high as the length of the dipole and several times as wide.

The dipoles 2 and 3 are adapted to receive equally well waves having vertical polarization as well as waves having horizontal polarization. This operation is accomplished without requiring any position change or shifting of the dipole. In order to accomplish this in accordance with our invention the dipoles 2 and 3 are mounted on the reflecting screen 4 so that they are at substantially a angle with both the vertical and the horizontal. The dipoles also extend in a vertical plane substantially parallel to the plane in which the reflector extends. In this angular position the dipoles respond equally well to vertically and horizontally polarized waves, as will be seen from Figs. 3 and 4 which respectively show actual results obtained with an antenna system of the type hereinabove described in response to horizontally and vertically polarized waves respectively. It will be seen that the null is very sharply and clearly defined in both instances. The irregularity of the two lobes was due to an unbalance in the actual system employed. In order to rotate the pattern of the antenna system the reflector 4 rotates around a vertical axis such as4 axis l5 shown in Fig.

\ 3 2, thus the antenna system scans the 'entire azimuth, the "null being used for directional indications.

While we have described our invention in connection with the direction'iinder receiving system, it will be apparent that the antenna. system of our invention may be employed in a transmission system such as for example in a beacon system.

Accordingly, while we have described above the principles of our invention in connection with speciilc apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope ot our invention as defined in the accompanying claims.

We claim: f

1. In a direction tlnder ,system a pair o! dipoles extending at an angle of substantially 45 to the vertical and spaced apart, a planar reector adjacent said dipoles and lying in a substantially vercal plane parallel to the plane in which said poles lie, and means ionconnecting said dipoles in phase opposition. l

2. In a directional antenna system, a pair of spaced apart antenna elements each extending at an angle to the vertical at substantially less than 90 parallel to each other, said elements being spaced a distance apart equivalent to 180 or less at the mean-frequency at which said system is designed to operate, means ior coupling said elements together in phase opposition. and a reflector adjacent said elements and extending in a vertical plane.

3. A direction finding system comprising a pair of dipole antenna elements extending at substantially the same angle, other than 90 to the vertical. a planar reflector adjacent to said elements and lying in a vertical plane substantially parallel to a plane in which said elements lie, said reflector andv antenna elements being mounted for rotation about a vertical axis, a receiver,l an indicator, means for applying the output of said antenna elements in phase opposition through said receiver to said indicator.

,- l HENRI G. BUSIGNIES.

NATHAN MARCHAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Lieb et al June 1, 1937 2,311,435

Gerhard Feb. 16, 1943 Luaenla Mar. 27, 1934` 

